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The substructure for a wooden terrace is essential in order to be able to lay the elements without any problems. The distance between the support beams is particularly important in order to ensure sufficient stability.
In a nutshell
- ideal distance depends on board thickness
- reduces the risk of breakage
- increases stability
- helps to determine the amount of material
- Ground clearance protects against weather influences
Support beams: ideal spacing
In order to ensure good stability for the substructure of the wooden terrace, it is important to plan the right distance between the individual beams. They must not be too far apart, otherwise there is a possible risk of breakage. This is because the planks could sag due to too much spacing. Likewise, too short a distance is not worthwhile, otherwise you will need far too much material. The following values between the individual beams have therefore been established as the ideal distance, depending on the material thickness of the decking boards:
- 40 cm: thickness up to 25 mm
- 50 cm: Thickness from 25 mm
This is used as the ideal spacing for the substructure between the individual beams. This point is important because often the overall length is misclassified when measuring from the center of the beam. As a result, you either order too much or too little material. To clarify this point and to help you with the planning, you will find an example of a four meter wide terrace (board thickness 20 mm), for which beams with a width of seven centimeters are used for the substructure:
- Total width in cm / (bar width in cm + bar spacing in cm) = amount of bars required
- 400 cm / (7 cm + 40 cm) = amount of beams needed
- 400cm / 47cm = 8.5 beams
- Order 9 beams
Tip: Don't forget the distance to the wall so that the substructure of the wooden terrace does not lie directly against it. A distance of 15 to 30 millimeters is perfectly sufficient for this.
Note ground clearance
You not only have to consider the distance between the individual bars. The substructure for a wooden terrace, like the planks, must not lie directly on the ground. Otherwise, the material used will be adversely affected by the moisture and will have to be replaced over time. Five to six centimeters are recommended as the ideal distance from the floor to the substructure. This offers several advantages:
- water flows freely
- good air circulation
At the same time, the ground clearance in combination with the thickness of the beams indicates the height of the substructure. This does not include the selected decking boards. If the decking boards are included, it would be the total height of the entire deck, not just the substructure. If you use beams with a thickness of 4.5 cm, for example, calculate the ground clearance for the substructure as follows:
- Ground clearance in cm + bar thickness in cm = total height in cm
- 5 or 6cm + 4.5cm = 9.5 or 10.5cm
Notice: Be sure to include the required gradient of two percent in your planning. The substructure for your wooden terrace must not be completely level so that rain and melt water can run off.
Distance on push?
Depending on the extent of the planned wooden terrace, you may have to butt-join the support beams that are too short to the substructure. What is meant by this? Butt joint means the seamless laying of two support beams for the substructure in order to achieve the required length. There is no distance between the bars, so you don't have to pay attention to this. You connect them with flat connectors. For this reason it is important that the material thickness of the beams is exact. In addition, the beams must rest on a foundation foot or stone at the connection point. Otherwise there is a risk that the substructure will break at this point.
Notice: Never lay the individual rows with a single, continuous butt joint. Meanwhile, to improve the stability of this method, you need to lay them staggered to each other.
frequently asked Questions
Which materials can be used for the substructure?The substructure can be made of either wood, aluminum or stainless steel. If you choose wood, weatherproof types are recommended. These include, for example, oak, robinia or larch wood. Many tropical woods such as Bangkirai are also recommended. Aluminum and steel are offered as prefabricated support beams.
What is a floating substructure?If you opt for the floating construction, do not fix the substructure to the subsoil. The substructure for your wooden terrace is built in advance and placed using accessories such as terrace pads. The wooden floorboards are then screwed to the substructure. This is possible due to the crosswise laying method.
Can the substructure be placed on lawns?Yes, but the floor must be fixed beforehand so that the wooden deck does not sink into the earth or shift due to the weight. A pit is dug, filled with a 20 centimeter high layer of gravel or sand and compacted. Compact another layer (5 cm) of gravel or grit, cover with weed fleece and lay foundation slabs.